The IEEE 802.15.4e standard, published in 2012, includes support for Low Latency Deterministic Networks (LLDNs). An LLDN is defined as a personal area network (PAN) organized as a star network with a superframe structure and using LLDN frames. The LLDN mechanism of the IEEE 802.15.4 brings many benefits for certain applications. These applications require low-latency and reliable periodic transmissions from sensor devices (such as ECG sensors) to the PAN coordinator. The LLDN superframe structure allows usage of implicit addressing which greatly reduces the media access control (MAC) control overhead. It also provides guaranteed channel access at a LLDN device's pre-assigned time slot, so that critical sensor data can be reported to the coordinator in a timely manner.
An LLDN superframe contains multiple time slots for data transmissions/retransmission. According to the current standard, if a device does not need to retransmit a failed frame occurred in the previous superframe, it only needs to transmit once in its own uplink time slot (assuming it has data to send), but it has to remain powered on during other devices' uplink time slots or bidirectional time slots.